Abstract: Cleaning plant is an important component of corn combine harvester, the airflow velocity from the exit of fan should keep uniformity for improving grain cleanness and reducing the clear selections loss. The low-blast and medium-speed centrifuge fan, which mostly adopted in the corn combine, has bad homogeneity on the direction of vane width. The results of the test on the combined cleaning fan show that the airflow speed standard deviation is 0.5727 and beta coefficient is 5% and stability beta is 95%,　which is lower than centrifuge fan, and stability beta is high. At the same time, the airflow speed distribution on the exit of combined fan is that the lower speed locates in the double end and the higher speed locates in the middle, the centrifuge fan is on the contrary, which has greatly improved the uniformity of the airflow speed in the exit fan.